Freshwater bivalve

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Freshwater bivalves are molluscs of the order Bivalvia that inhabit freshwater ecosystems. They are one of the two main groups of freshwater molluscs, along with freshwater snails.

Contents

The majority of bivalve molluscs are saltwater species that live in the marine habitats, but a number of families have evolved to live in fresh water (and in some cases, also in brackish water). These belong to two different evolutionary lineages, i.e. freshwater mussels and freshwater clams, and the two groups are not closely related. Freshwater bivalves have a simple morphology that varies among taxa, and are distributed around most regions of the world.

Freshwater bivalve species vary greatly in size. Some pea clams (genus Pisidium ) have an adult size of only 3 mm (0.12 in). In contrast, one of the largest species of freshwater bivalves is the swan mussel from the family Unionidae; it can grow to a length of 20 cm (7.9 in), and usually lives in lakes or slow-flowing rivers. Freshwater pearl mussels are economically important as a source of pearls and mother of pearl. While some species are short-lived, others can be quite long-lived, with some species registering longevity in the hundreds of years. [1]

Freshwater bivalves can thrive in many different types of habitats, ranging from small ditches and ponds to large lakes, rivers, canals and wetlands. The ecology of freshwater bivalves varies among species with regards to differences in reproduction and predation. In spite of their variety of ecosystems, freshwater bivalves are some of the most endangered species on the planet. In North America, for instance, many freshwater mussel species have gone extinct, and of those remaining, 65 percent are rated as endangered, threatened or vulnerable. Droughts, forest clearing, farming, use of dams for water management, and changes in water temperature can all pose threats to freshwater bivalve populations. Restoration efforts focus on rebuilding lost mussel populations in the wild and using those mussels to improve and protect water quality and restore broader ecosystems. [2] [3]

Morphology

External

Freshwater bivalves, as their name implies, have a protective exoskeleton composed of two half-shells or "valves", connected via a soft ligament along a hinge. [4] These two valves are non-living, composed of both organic and inorganic substances that make up three major valve layers. [4] The first, outermost layer is the thin epidermis (periostracum), followed by a second prismatic layer, containing calcium carbonate. [4] The third and innermost layer is also the thickest and is most commonly referred to as the mother of pearl--- a widely harvested source for the production of ornamental buttons. [4] The external appearances of these shells can be extremely variable when comparing members of different families, genus, etc., as well as intraspecies. [4] Valve surface appearances can range from smooth to dramatically sculpted, showcasing ornamental pustules, pimples, grooves, and ridges. [4] The overall shape of the valve can also vary drastically, from laterally compressed and narrow, to wide and globular. [4]

Internal

The mantle is a multifunctional, generally thin and fragile structure that line bivalve interiors and encloses their bodies. This structure secretes the shell, contains respiratory organs and facilitates feeding. The cavity that exists between the mantle and other soft tissues is aptly named the mantle cavity. [4]

Within the mantle cavity on either side of the foot are the gills. The inner gills are adjacent to the foot and the outer gills nearest to the mantle and shell. As expected, these gills mainly act as a respiratory structure, performing gas exchange but can also facilitate filter feeding. Water enters the mantle cavity via an incurrent siphon, and passes over the gills where food particles are trapped by secreted mucus. [4]

Anterior and posterior adductor muscles connect the left and right valves, facilitating shell opening and closure. [4] The less major anterior and posterior retractor muscles extend from the shell and attach the body to a structure called the foot. [4] This muscular foot is typical of most bivalves, extending anteriorly between the valves (via an anterior protractor muscle) and aiding in locomotion, burrowing and anchorage (holdfast). [4]

Distribution

The exact distribution of every freshwater bivalve genera cannot be ascertained because of the lack of data in certain areas of the world like Africa and South America, but freshwater bivalves have been found in all of Earth's biogeographic realms, except for the Antarctic biogeographic realm. [5] [6] There are 40 freshwater bivalve representative genera in the Palearctic biogeographic realm, 59 in the Nearctic, 23 in the Afrotropical, 51 in the Neotropical, 47 in the Oriental, 13 in the Australasian, and two in the Pacific Ocean Islands, for a total of 206 freshwater bivalve genera currently identified in the world. [5] Freshwater bivalves are native to the Oriental biogeographic realm and to the southeastern United States and have been introduced to other regions, specifically the two genera in the Pacific Ocean Islands were introduced from Hawaii. [5]  As new methods of identifying and locating freshwater bivalves improve, the distribution of where these freshwater bivalves occur can become more apparent.

Taxonomy

The study of freshwater bivalves predates Aristotle and has since been in a state of constant flux and dispute, regarding their identification and classification. [5] As time has progressed, so too have different techniques and technologies that allow scientists to more comprehensively study the assemblages of organisms in the natural world, freshwater bivalves included. Modern genetic analysis has had major applications in the modern history of taxonomy and has been since utilized in the advancement of freshwater bivalve classification by allowing researchers to identify commonly used genes within these groups. [5] The most commonly used method of identification/classification utilizes an exceptionally diverse set of ever-expanding morphological features, ranging from shell anatomy, variations in internal soft tissue, degrees of mantle fusion, to larval stage development. [5]

Orders and families

Unionida

The Unionida, of worldwide distribution, are the pearly freshwater mussels. All reproduce by means of a larval stage that is parasitic on a fish or salamander. Many species are utilized as sources of mother-of-pearl.

Families:

Veneroida

The Veneroida is a large group of bivalve "clams", most of which are marine. However, several families occur in fresh and brackish waters.

Families:

Reproduction

Mechanisms

Freshwater Bivalves can utilize either ovoviviparous or viviparous reproduction strategies, ovoviviparous meaning that embryos develop and grow in eggs inside the female until they are ready to be released. The embryos get nutrition from egg yolk, but are not connected to the mother by a placental connection. Viviparous meaning embryos develop inside the body of a female and usually gain nutrition by a placental connection. Females tend to have a single reproductive spawning period (when the ova moves to the gills) while males tend to have two spawning periods (a release of sperm into the water column). [7] Females have highest ova, or mature female reproductive cells, during September with a gradual decrease until December. Males spawn between September and December with a second spawning period between May and July. [7] Males release their sperm into the water column for females to accept. Females take up the sperm along with water through their circulatory system and have the potential to become fertilized when the sperm meets the ova. In contrast to Marine Bivalves, most female freshwater bivalve species hold the fertilized embryos until they develop into larvae when they are released into the water. [8]

Larvae

Once larvae are released into the water column they become semi-parasitic and attach to the gills of freshwater fish. They attach to a host where they grow into juvenile adults while doing little to no damage to the fish host. [8] The order Unionidae have an obligate parasitic larval stage where the larvae are attached to the gills, fins or the body of a particular host fish. [5]

Microbial water composition and sediment composition are important in larval nutrition. [9]

Predation

Invasive species pose a risk to freshwater bivalve populations. Specifically two invasive species of crayfish, Procambarus clarkii and Pacifastacus leniusculus, are predators of the freshwater bivalve species Anodonta anatina. [10] In general, freshwater bivalves have predators such as raccoons, otters, some species of fish, and some species of turtles.

Droughts, floods, and heat waves are a few examples of major climatic events that are happening more frequently because of the global changing climate. This is a huge killer of freshwater bivalve populations. [11]

Ecosystem function

Freshwater bivalves are important bioindicators of freshwater ecosystems because they are the connection between the water column and the benthos, for they can provide information on the quality of the water based on the particles and toxins that bioaccumulate in the tissue of bivalves. [12] Freshwater bivalves are filter feeders and provide an ecological service by improving water quality in the bodies of water they inhabit, such as rivers, lakes, and wetlands. [5] Water quality is improved by filtering out fine particles of silt, organic matter, and heavy metals as well as bacteria and phytoplankton in the water column to reduce turbidity. [5]

Freshwater bivalves are also important in the process of nutrient cycling because they deposit organic matter in the sediment through biodeposition created from the fine particles they filter in. Organic matter can be deposited in the sediment as feces or dead matter, and depending on if the right environmental conditions are present, such as hypoxia, sediment denitrification can occur, releasing nitrogen back into the atmosphere. [13] However, other organisms are unable to utilize this inorganic form of nitrogen, so freshwater bivalves can also excrete dissolved nutrients in an accessible form for primary producers and consumers to assimilate. [13] Any nutrients that were retained by the freshwater bivalve through its lifespan for building shell tissue can serve as a long-term nutrient storage in the benthos when the organism dies, depending on water chemistry and flow conditions. [13] Considering freshwater bivalves can filter particles and process nutrients in the nutrient cycle, there are other species of freshwater bivalves that have more specialized ecosystem functions as well as different vulnerabilities.

Threats to bivalves

Invasive species

Example of Dreissena polymorpha (Zebra Mussel). Dreissena polymorpha3.jpg
Example of Dreissena polymorpha (Zebra Mussel).

Dreissenidae are a family of freshwater mollusks considered to be an invasive species found across Eurasia and North America. [14] The most common types of dreissenids are Dreissena polymorpha (Zebra mussel) and Dreissena rostriformis (Quagga mussel). [14] These mussels damage both ecological systems and human infrastructure. In North America, biofouling caused by dreissenids created 267 million dollars’ worth of damage between 1989 and 2004. [14] When introduced to freshwater ecosystems, dreissenids lead to a decline in indigenous marine animal populations and are also known for causing benthic algae and cyanobacterial blooms. [14] The total impact of dreissenids on freshwater ecosystems is still unknown.

Anthropogenic impacts

Pollution, human disturbance, invasive species, and ecosystem modification are the main threats to freshwater bivalves. [15] In North America freshwater bivalves are extremely threatened, with 202 of 300 species considered critical, possibly extinct, or extinct. [15] Of the dangers facing freshwater bivalves, eighty-five percent of them are considered to be “ongoing threats”. [15] Ecosystem modification and pollution are currently the two biggest threats to molluscs and gastropods in Palearctic and Nearctic ecozones. [15] Pollution is the dominant issue for these animals in the Afrotropic and Indomalayan biogeographic realms. [15] For the Neotropics and Australasia biogeographic realms, ecosystem modification has the largest impact on freshwater bivalve species. [15] Hydropower plants and dams are two examples of human ecosystem modification which contributes to loss of habitat as well as changes to channel morphology, river and floodplain connectivity and nutrient limitation. [16] Rates of extinction among freshwater bivalves are higher than those of terrestrial groups which share the same ecosystem. [15] Among those bivalves, freshwater gastropods are the most highly threatened due to smaller species distribution. [15] Freshwater bivalves are at a heightened risk for endangerment and extinction because of the connectivity of river systems. [15] Anthropogenic impacts on rivers spread throughout the whole ecosystem. [15]  

Related Research Articles

<span class="mw-page-title-main">Mussel</span> Type of bivalve mollusc

Mussel is the common name used for members of several families of bivalve molluscs, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which are often more or less rounded or oval.

<span class="mw-page-title-main">Bivalvia</span> Class of molluscs

Bivalvia, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bivalves have no head and they lack some usual molluscan organs, like the radula and the odontophore. The class includes the clams, oysters, cockles, mussels, scallops, and numerous other families that live in saltwater, as well as a number of families that live in freshwater. The majority are filter feeders. The gills have evolved into ctenidia, specialised organs for feeding and breathing. Most bivalves bury themselves in sediment, where they are relatively safe from predation. Others lie on the sea floor or attach themselves to rocks or other hard surfaces. Some bivalves, such as the scallops and file shells, can swim. Shipworms bore into wood, clay, or stone and live inside these substances.

<i>Mytilopsis sallei</i> Species of bivalve

Mytilopsis sallei, the black-striped mussel, is a small marine bivalve mollusc in the family Dreissenidae, the false mussels.

The Dreissenidae are a family of small freshwater mussels, aquatic bivalve molluscs. They attach themselves to stones or to any other hard surface using a byssus. The shells of these bivalves are shaped somewhat like those of true mussels, and they also attach themselves to a hard substrate using a byssus; however, this group is not at all closely related to true mussels, being more closely related to the venus clams (Veneridae).

<span class="mw-page-title-main">Unionidae</span> Family of molluscs

The Unionidae are a family of freshwater mussels, the largest in the order Unionida, the bivalve molluscs sometimes known as river mussels, or simply as unionids.

<span class="mw-page-title-main">Palaeoheterodonta</span> Subclass of bivalves

Palaeoheterodonta is a subterclass of bivalve molluscs. It contains the extant orders Unionida and Trigoniida. They are distinguished by having the two halves of the shell be of equal size and shape, but by having the hinge teeth be in a single row, rather than separated into two groups, as they are in the clams and cockles.

<i>Corbicula fluminea</i> Species of mollusc

Corbicula fluminea is a species of freshwater clam native to eastern Asia which has become a successful invasive species throughout the world, including North America, South America, Europe, and New Zealand. It is native to freshwater environments of Eastern Asia, including Russia, Thailand, the Philippines, China, Taiwan, Korea, and Japan. C. fluminea also occurs naturally in freshwater environments of Africa. Corbicula fluminea is commonly known in the west as the Asian clam, Asiatic clam, or Asian gold clam. In Southeast Asia, C. fluminea is known as the golden clam, prosperity clam, pygmy clam, or good luck clam. In New Zealand, it is commonly referred as the freshwater gold clam.

<i>Corbicula</i> Genus of bivalves

Corbicula is a genus of freshwater and brackish water clams, aquatic bivalve mollusks in the family Cyrenidae, the basket clams. The genus name is the Neo-Latin diminutive of Latin corbis, a basket, referring to the shape and ribs of the shell.

<span class="mw-page-title-main">Margaritiferidae</span> Family of bivalves

Margaritiferidae is a family of medium-sized freshwater mussels, aquatic bivalve molluscs in the order Unionida. It is the most threatened of all unionid families.

<i>Sinanodonta woodiana</i> Species of bivalve

Sinanodonta woodiana, the Chinese pond mussel, Eastern Asiatic freshwater clam or swan-mussel, is a species of freshwater mussel, an aquatic bivalve mollusk, in the family Unionidae.

<span class="mw-page-title-main">Unionida</span> Order of bivalves

Unionida is a monophyletic order of freshwater mussels, aquatic bivalve molluscs. The order includes most of the larger freshwater mussels, including the freshwater pearl mussels. The most common families are the Unionidae and the Margaritiferidae. All have in common a larval stage that is temporarily parasitic on fish, nacreous shells, high in organic matter, that may crack upon drying out, and siphons too short to permit the animal to live deeply buried in sediment.

<i>Cyprogenia</i> Genus of bivalves

Cyprogenia is a genus of freshwater mussels, aquatic bivalve mollusks in the family Unionidae.

<i>Lampsilis</i> Genus of bivalves

Lampsilis is a genus of freshwater mussels, aquatic bivalve mollusks in the family Unionidae, the river mussels. There are over 100 species in the genus.

<i>Lampsilis ovata</i> Species of bivalve

Lampsilis ovata, or pocketbook mussel, is a species of freshwater mussel, a bivalve mollusk in the family Unionidae, the river mussels. This species is endemic to eastern North America.

<span class="mw-page-title-main">Glochidium</span> Larvae of bivalves

The glochidium is a microscopic larval stage of some freshwater mussels, aquatic bivalve mollusks in the families Unionidae and Margaritiferidae, the river mussels and European freshwater pearl mussels.

<span class="mw-page-title-main">Bivalve shell</span> Seashell

A bivalve shell is part of the body, the exoskeleton or shell, of a bivalve mollusk. In life, the shell of this class of mollusks is composed of two hinged parts or valves. Bivalves are very common in essentially all aquatic locales, including saltwater, brackish water, and freshwater. The shells of bivalves commonly wash up on beaches and along the edges of lakes, rivers, and streams. Bivalves by definition possess two shells or valves, a "right valve" and a "left valve", that are joined by a ligament. The two valves usually articulate with one another using structures known as "teeth" which are situated along the hinge line. In many bivalve shells, the two valves are symmetrical along the hinge line—when truly symmetrical, such an animal is said to be equivalved; if the valves vary from each other in size or shape, inequivalved. If symmetrical front-to-back, the valves are said to be equilateral, and are otherwise considered inequilateral.

<i>Villosa iris</i> Species of bivalve

Villosa iris, the rainbow mussel or rainbow-shell, is a species of freshwater mussel, an aquatic bivalve mollusk in the family Unionidae, the river mussels. In 2018, Watters proposed to move the species into a new genus, Cambarunio.

<i>Mytilopsis leucophaeata</i> Species of bivalve

Mytilopsis leucophaeata is a species of small bivalve mollusc in the false mussel family, Dreissenidae. It is commonly known as Conrad's false mussel or the dark false mussel.

<span class="mw-page-title-main">Freshwater mollusc</span>

Freshwater molluscs are those members of the Phylum Mollusca which live in freshwater habitats, both lotic such as rivers, streams, canals, springs, and cave streams and lentic such as lakes, ponds, and ditches.

<i>Velesunio wilsonii</i> Species of bivalve

Velesunio wilsonii is a species of freshwater mussel endemic to Australia and comes from the Hyriidae family. Velesunio wilsonii mussels have a thick, dark shell that are sometimes flaky and mostly closed. Velesunio wilsonii have a fleshy foot that sometimes extends outside of the valves. The shell of the Velesunio wilsonii varies from oblong to a symmetrical circle. Velesunio wilsonii size ranges from 40 mm to 120 mm.

References

  1. ↑ Haag, W.R., and A.L. Rypel. 2011. Growth and longevity in freshwater mussels: evolutionary and conservation implications. Biological Reviews 86: 225-247.
  2. ↑ Levy, Sharon (June 21, 2019). "The hidden strengths of freshwater mussels". Knowable Magazine. doi: 10.1146/knowable-062019-1 .
  3. ↑ Vaughn, Caryn C.; Hoellein, Timothy J. (2018-11-02). "Bivalve Impacts in Freshwater and Marine Ecosystems". Annual Review of Ecology, Evolution, and Systematics. 49 (1): 183–208. doi: 10.1146/annurev-ecolsys-110617-062703 . S2CID   91784258 . Retrieved 25 June 2021.
  4. 1 2 3 4 5 6 7 8 9 10 11 12 Howells, Robert G.; Neck, Raymond W.; Murray, Harold D.; Inland Fisheries Division, Texas (1996-06-05). Freshwater Mussels of Texas By Robert G. Howells, Raymond W. Neck, and Harold D. Murray. ISBN   978-1-885696-10-6. Archived from the original on 2021-11-02. Retrieved 2020-12-05.
  5. 1 2 3 4 5 6 7 8 9 Bogan, Arthur E. (2008). "Global diversity of freshwater mussels (Mollusca, Bivalvia) in freshwater". Hydrobiologia. 595 (1): 139–147. doi:10.1007/s10750-007-9011-7. ISSN   0018-8158. S2CID   38660332.
  6. ↑ Lopes-Lima, Manuel; Froufe, Elsa; Do, Van Tu; Ghamizi, Mohamed; Mock, Karen E.; Kebapçı, Ümit; Klishko, Olga; Kovitvadhi, Satit; Kovitvadhi, Uthaiwan; Paulo, Octávio S.; Pfeiffer, John M. (2017). "Phylogeny of the most species-rich freshwater bivalve family (Bivalvia: Unionida: Unionidae): Defining modern subfamilies and tribes". Molecular Phylogenetics and Evolution. 106: 174–191. doi:10.1016/j.ympev.2016.08.021. hdl: 10198/15272 . PMID   27621130. S2CID   4199349.
  7. 1 2 Beasley, C.R (2000). REPRODUCTIVE CYCLE, MANAGEMENT AND CONSERVATION OF PAXYODON SYRMATOPHORUS (BIVALVIA: HYRIIDAE) FROM THE TOCANTINS RIVER, BRAZIL. Universidade Federal do Pará, Campus de Bragança.
  8. 1 2 "Developmental Behaviors". www.reed.edu. Retrieved 2020-11-14.
  9. ↑ Sicuro, Benedetto (2015-03-19). "Freshwater bivalves rearing: a brief overview". International Aquatic Research. 7 (2): 93–100. doi: 10.1007/s40071-015-0098-6 . hdl: 2318/1525314 . ISSN   2008-4935. S2CID   84793001.
  10. ↑ Meira, Alexandra; Lopes-Lima, Manuel; Varandas, Simone; Teixeira, Amílcar; Arenas, Francisco; Sousa, Ronaldo (2019). "Invasive crayfishes as a threat to freshwater bivalves: Interspecific differences and conservation implications". Science of the Total Environment. 649: 938–948. Bibcode:2019ScTEn.649..938M. doi:10.1016/j.scitotenv.2018.08.341. hdl: 10198/17915 . ISSN   0048-9697. PMID   30179822. S2CID   52170881.
  11. ↑ Ilarri, M.I.; Souza, A.T.; Sousa, R. (2015-03-01). "Contrasting decay rates of freshwater bivalves' shells: Aquatic versus terrestrial habitats". Limnologica. 51: 8–14. doi: 10.1016/j.limno.2014.10.002 . hdl: 1822/49090 . ISSN   0075-9511.
  12. ↑ Lopes-Lima, Manuel; Teixeira, Amílcar; Froufe, Elsa; Lopes, Anabela; Varandas, Simone; Sousa, Ronaldo (2014). "Biology and conservation of freshwater bivalves: past, present and future perspectives". Hydrobiologia. 735 (1): 1–13. doi:10.1007/s10750-014-1902-9. hdl: 1822/31319 . ISSN   0018-8158. S2CID   8072252.
  13. 1 2 3 Buelow, Christina A.; Waltham, Nathan J. (2020). "Restoring tropical coastal wetland water quality: ecosystem service provisioning by a native freshwater bivalve". Aquatic Sciences. 82 (4): 77. doi:10.1007/s00027-020-00747-7. ISSN   1015-1621. S2CID   224928249.
  14. 1 2 3 4 Higgins, S. N.; Zanden, M. J. Vander (2010). "What a difference a species makes: a meta—analysis of dreissenid mussel impacts on freshwater ecosystems". Ecological Monographs. 80 (2): 179–196. doi:10.1890/09-1249.1. ISSN   0012-9615. JSTOR   27806882.
  15. 1 2 3 4 5 6 7 8 9 10 Böhm, Monika; Dewhurst-Richman, Nadia I.; Seddon, Mary; Ledger, Sophie E. H.; Albrecht, Christian; Allen, David; Bogan, Arthur E.; Cordeiro, Jay; Cummings, Kevin S.; Cuttelod, Annabelle; Darrigran, Gustavo (2020-09-12). "The conservation status of the world's freshwater molluscs". Hydrobiologia. 848 (12–13): 3231–3254. doi:10.1007/s10750-020-04385-w. hdl: 1854/LU-8689344 . ISSN   0018-8158. S2CID   224884712.
  16. ↑ Sousa, Ronaldo; Ferreira, André; Carvalho, Francisco; Lopes-Lima, Manuel; Varandas, Simone; Teixeira, Amílcar; Gallardo, Belinda (2020-06-01). "Small hydropower plants as a threat to the endangered pearl mussel Margaritifera margaritifera". Science of the Total Environment. 719: 137361. Bibcode:2020ScTEn.719m7361S. doi:10.1016/j.scitotenv.2020.137361. hdl: 10198/21930 . ISSN   0048-9697. PMID   32135319. S2CID   212568826.
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